Coming from the 7D to the 5D Mark III, I am amazed at the ISO noise performance. Here are some shots I took of the Hulk from my kid's Happy Meal at high ISO settings starting at 6400 and going up to H2 (102400). Even though you can see a slight degradation in sharpness and increase in noise, I could be perfectly happy shooting with 12800 ISO on the 5D3 if it was called for and even 25600 when I had to. The H1 and H2 could provide useable shots in emergency situations (Total EM blackout, sun turning to sackcloth and moon to blood, etc.)

Ultimately, you'll have to decide for yourself what is acceptable and not acceptable.

Regarding high ISO hulk shots above. For me, it is not the best way to show quality of High ISO by these examples. With these lighting, you already get good exposure at 6400, that means, with the same lighting on higher ISO, All parts of the image is within the limit of ISO sensor bucket if you will.

Its a different scenario where in, you are in dark places, then even at 25600 ISO, u still get 1/2 stop underexpose image.

I am an amateur with less than a month experience on DSLR.What I am saying is, for me, you can not gauge ISO performance in well lighted conditions, also,the subject in your example is too big and maybe detail less in the first place.

I have not intelligently shoot my 6D yet, unlike my G12, I know its peak.Hopefully soon, I will know its peak performance.. and see what peak is peak.

The lighting for the Hulk shots wasn't very bright. Actually, it was fairly dimly lit. I agree that you'll get different noise and color banding patterns in different lighting conditions, so no tests or photos online are going to show you how your photos are going to turn out. The point is how much (or little) noise you are getting at these high ISO settings, and there aren't many systems out there that can touch the ISO noise performance of the current Canon FF cameras.

I have 7D. The largest part of my photos are shot at ISO 100-200. If there is a need i go up to ISO 1000-1200 in order to avoid blurred pictures. However, when i was on vacation in Roma and shoot in quite dark churches I increased ISO up to 3200 and good really good pictures (of course, there was noice, which was expected).

In other cases I use flash or do not shoot at all I have tripod, however, never used it as it is quite inconvenient to carry it. In specific cases (shooting night photos, landscapes, etc.) of course I would use tripod.

Regarding aperture: when shoting portraits I usually go to 2.8, but in other cases when more of DoF is required I shoot at 5.6 and higher.

I have a 5D Mark III and ayhting up to ISO 6400 looks superb. I will use ISO 12800 and 25600, using noise reduction tends to produce good images even at these high settings. I do not like to go any higher than 25600.

From the replies I've seen on this topic, people tend to shoot at whatever ISO and aperture gets the shot. Granted, across the board, lower ISO is better, but there doesn't really seem to be a trend where people would consistently not use high ISO, the shot is more important.

So I guess you could say, don't worry about it too much and get the shot instead.

The lighting for the Hulk shots wasn't very bright. Actually, it was fairly dimly lit. I agree that you'll get different noise and color banding patterns in different lighting conditions, so no tests or photos online are going to show you how your photos are going to turn out. The point is how much (or little) noise you are getting at these high ISO settings, and there aren't many systems out there that can touch the ISO noise performance of the current Canon FF cameras.

Thanks, I understand that. When did you get your mark iii? I will be glad if you can share more 128 and 256 ISO pictures showing noise and details performance.I will post too, if I have something to show.

Thanks for all the inputs.I really don't have time or should I say lazy on comparing each settings of 6D.Using 6D, I have used Av mode since.

This is what I will do, i will shoot in manual mode and set the following for normal shots:Set shutter speed to 1/60, aperture to 5.6, ISO set to minimum or less than 8000.I will push shutter speed as low as 1/15 and see if I can manage the shake.I will push aperture until F2.0 and will expect capture still sharp.

After knowing the min shutter speed and minimum aperture i desire.I will play with 128 and 256, checked noise and details. Then I will know, what dark is dark for this camera.I will post as soon as I get something.

I have no problem maxing out my 1D Mark IIN, I'm happy shooting at 3200 ISO (H1) once my exposure is set perfectly in camera, it doesn't give much leeway for editing the exposure of the RAW files.

Using a 24-70mm F/2.8 I can get a keeper rate of about 70% when shooting at 1/30th. I typically shoot at F/2.8 all the time, regardless of bokeh. Unless I'm doing a group shot or specifically looking for an image to be extra sharp (like a picture which contains signs with writing or an environmental portrait) then I'll stop down to F/4 or F/5.6.

If I want to increase DOF then I push to F4 to F8 max.If I want to freeze motion then I push to 1/125.If I want to increase exposure then . decrease shutter speed to 1/45 . or push ISO up to 8000 to 10k Max . or enlarge aperture up to 1.8.

In extreme Low light then . decrease shutter speed up to 1/30 . max out aperture to 1.8 . Increase ISO as necessary.

Which one is better? increase ISO from 6400 to 10k or push aperture to F1.8.